Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.70	7.348%	$141.3773	$141.38	$141.40	$141.40
Purchase #2	$30.89	13.566%	$35.0805	$35.08	$35.10	$35.10
Purchase #3	$72.39	11.660%	$80.8307	$80.83	$80.85	$80.80
Purchase #4	$172.40	11.445%	$192.1312	$192.13	$192.15	$192.10
Purchase #5	$243.95	10.287%	$269.0451	$269.05	$269.05	$269.00
Purchase #6	$153.30	3.397%	$158.5076	$158.51	$158.50	$158.50
Purchase #7	$155.32	11.300%	$172.8712	$172.87	$172.85	$172.90
7 purchase totals =	$959.95		$1,049.8436	$1,049.85	$1,049.90	$1,049.80